Positive displacement pumps are one of the most commonly used pumps in the industry.
Here is an example of a Viking positive displacement pump to demonstrate how it works.
Viking’s simple “gear-within-a-gear” principle has only two moving parts. The first part is the positive displacement of the liquid that is accomplished by filling all the spaces completely between the teeth of the rotor and idler gears.
With every revolution of the pump shaft, a certain amount of the liquid enters the pump through the suction port. The liquid then goes on to fill the spaces between the teeth of the rotor and the idler. The crescent on the pump head then separates the flow of the liquid as it effortlessly moves toward the discharge port.
The idler gear, which carries the liquid between its teeth and the inside surface of the crescent is then rotated on the pin which is supported by the pump head.
The rotor gear transports the liquid between its teeth, which travels between the casing and the outside surface of the crescent which is connected to the pump shaft. The four diagram drawings illustrated below show how a positive displacement pump works.